Sep 17, 2011

Not all stars are loners. In our home galaxy, the Milky Way, about half of all stars have a companion and travel through space in a binary system. But explaining why some stars are in double or even triple systems while others are single has been something of a mystery. Now a team of astronomers from Bonn University and the Max-Planck-Institute for Radio astronomy (also in Bonn) think they have the answer -- different stellar birth environments decide whether a star holds on to its companion.

The scientists publish their results in a paper in the journal Monthly Notices of the Royal Astronomical Society.

Stars generally do not form in isolation but are born together in groups within clouds of gas and dust or nebulae. These stellar labour rooms produce binary star systems, which means that virtually all newborn stars have a companion. Most of these groups of stars disperse quickly so that their members become part of the Galaxy. But why, then, are not all stars seen in the sky binaries, but only half of them?

Before the groups of stars disperse, binary stars move through their birth sites and the group studied how they interact with other stars gravitationally. "In many cases the pairs are torn apart into two single stars, in the same way that a pair of dancers might be separated after colliding with another couple on a crowded dance floor," explains Michael Marks, a PhD student and member of the International Max-Planck Research School for Astronomy and Astrophysics. The population of binaries is therefore diminished before the stars spread out into the wider Galaxy.

The stellar nurseries do not all look the same and are crowded to different extents, something described by the density of the group. The more binaries form within the same space (higher density groups), the more interaction will take place between them and the more binary systems will be split up into single stars. This means that every group has a different composition of single and binary stars when the group disperses, depending on the initial density of stars.

By using computer models to calculate the resulting composition of stars and binaries in regions of different densities, the Bonn astronomers know how different types of birth sites will contribute single stars and binary systems to the wider Galaxy. "Working out the composition of the Milky Way from these numbers is simple: We just add up the single and binary stars in all the dispersed groups to build a population for the wider Galaxy," says Kroupa.

Previously considered the ultimate marine survivors, and garnered the infamous designation of being the "cockroaches of the open waters," jellyfish are doling out the comeuppance to those who ever doubted their predatory skills. These aren't just gelatinous scavengers capable of living in overheated, acidic, and polluted seas - no, jellyfish are the new sharks.

The silent and slow-swimming gelatinous animals can punch just as much of an impact on the food web, and are taking over the top predator position in the ocean.

Even though its attack is not based on a visually coordinated strike, like that of a shark or tuna for example, jellyfish can eat their weight in crustacean prey making them predatory competitors with larger fish.

"In spite of their primitive life-style, jellyfishes exhibit similar instantaneous prey clearance and respiration rates as their fish competitors and similar potential for growth and reproduction," writes biological oceanographer José Luis Acuña of Spain and colleagues in this week's journal Science.

Indeed, in areas where overfishing and habitat destruction have depleted the large fish population, jellyfish have succeeded in taking over as top predators in the food web, the oceanographers report.

And the larger a jellyfish the more prey it can catch. Though a larger medusae, the top bell-shaped part of a jellyfish, slows the animal's swimming capabilities -- slow and large works just as well for running into unwitting prey. "Although larger bodies are less efficient for swimming, optimization analysis reveals that large collectors are advantageous if they move through the water sufficiently slowly," the authors write.

That means even the smaller ones can take over a top predator position that's vacant. "Most economically relevant fishes and trophically dominant jellyfishes are cruising predators, which hunt while swimming. Fishes have compact bodies and use their eyes to detect prey. In contrast, swimming medusae pulse their bells to create vortices that serve as a feeding current and transport prey to their tentacles and oral arms," explains the biologists.

The authors stress that part of the reason jellyfish weren't previously recognized for their predatory skills was because comparisons focused on size rather than carbon weight. If a jellyfish and a fish of equal size each entered a speed-eating contest the fish would always win. But jellyfish are made mostly of water. Judging based on body-size misses the big picture: "The competitive ability of a predator depends not only on prey capture and ingestion rates but on how efficiently the energy obtained translates into body growth and population buildup," they said.

To asses the "bioenergetic performance" of fishes, jellyfish, and their prey, the researchers based their comparisons on body carbon count. Their analysis showed that carbon-kilogram-to-carbon-kilogram jellyfish and fish come out even.

Sep 16, 2011

A new book about evolution that couldn't get published in the United States has won a Canadian book award.

On Wednesday the book, "Evolution: How We and All Living Things Came to Be," by Daniel Loxton, won the 2010 Lane Anderson Award in the young reader category for a book published in the field of science and written by a Canadian. Loxton's book was also a finalist for the prestigious Silver Birch Award earlier this year and is in the running for a third book award for Canadian children's nonfiction.

Loxton's book is, of course, not the first book devoted to evolution; for example, eminent biologist Richard Dawkins' "The Greatest Show on Earth: The Evidence for Evolution" came out in 2009. So why were American publishers reluctant to take Loxton's award-winning book?

Part of the answer is that, unlike most books on evolution, it's aimed at kids (suggested for ages 8 to 13). To those who dispute evolution, this smacks of indoctrination, not science education. Loxton told Discovery News that he approached several American publishers but was told that his book might be controversial and was "too hot a topic."

Evolution is certainly not controversial among scientists; it is instead a well-accepted and well-established process. Charles Darwin published "On the Origin of Species" in 1859, and evidence for evolution has grown more robust with each passing year.

Loxton begins "Evolution" by noting that different fossils are found in different geological strata -- a fact that suggested to early researchers that many now-extinct animals, such as dinosaurs, had once roamed the planet.

He goes on to discuss a wide variety of subjects related to evolution, from DNA to the alleged "dinosaur monster," mokele-mbembe, of central Africa. Along the way, he introduces new concepts such as species and mutation, often in the form of posed questions.

Darwin's experiments are briefly described, including his research into avian inbreeding and the variations found in beaks in isolated populations of Galapagos Island finches.

Evolution is all around us and relevant to our daily lives; for example, we need a new flu vaccine each year because the influenza virus evolves resistance to the previous year's drug.

Yet surveys show that a significant number of people (around 40 percent, depending on the poll question) have doubts about evolution. Many are creationists, who insist that evolution contradicts the Bible, despite the fact that Pope John Paul II issued a statement in 1996 saying the scientific evidence for evolution was well established ("more than a hypothesis") and compatible with Catholic faith.

Loxton, editor of a section devoted to teaching kids critical thinking in Skeptic magazine, was well aware of the efforts to inject creationism and "intelligent design" into public discussions about evolution. "Evolution" anticipates and addresses some of the most common anti-evolution fallacies (such as that the eye is too complex an organ to have evolved naturally).

Two early medieval skeletons were unearthed recently in Ireland with large stones wedged into their mouths -- evidence, archaeologists say, that it was feared the individuals would rise from their graves like zombies.

The skeletons, which were featured in a British documentary last week, emerged during a series of digs carried out between 2005 and 2009 at Kilteasheen, near Loch Key in Ireland by a team of archaeologists led by Chris Read from the Institute of Technology in Sligo, Ireland and Thomas Finan from the University of St. Louis.

The project recovered a total of 137 skeletons, although archaeologists believe that some 3,000 skeletons spanning from 700 to 1400 are still buried at the site.

The "deviant burials" were comprised of two men who were buried there at different times in the 700s.

One of the men was between 40 and 60 years old, and the other was a young adult, probably between 20 and 30 years old. The two men were laid side by side and each had a baseball-sized rock shoved in his mouth.

"One of them was lying with his head looking straight up. A large black stone had been deliberately thrust into his mouth," Chris Read, head of Applied Archaeology at IT Sligo, said.

"The other had his head turned to the side and had an even larger stone wedged quite violently into his mouth so that his jaws were almost dislocated," he added.

Initially, Read and colleagues thought they had found a Black Death-related burial ground. Remains of individuals buried at the end of the Middle Ages with stones stuck in their mouths have hinted at vampire-slaying rituals.

It was believed that these "vampire" individuals spread the plague by chewing on their shrouds after dying. In a time before germ theory, the stone in the mouth was then used as a disease-blocking trick.

Since the vampire phenomenon didn't emerge in European folklore until the 1500's, the archaeologists ruled out this theory for the 8th century skeletons.

"In this case, the stones in the mouth might have acted as a barrier to stop revenants from coming back from their graves," Read told Discovery News.

Revenants or the "walking dead" tended to be people who lived as outsiders in society, according to Read.

The two Irish men could have been considered potentially dangerous people, such as enemies, murderers, rapists or they could have been ordinary individuals who died suddenly from a strange illness or murder.

Anything outside the norm would have caused the community to fear that these people could have come back to life to harass their loved ones or others against whom they had a grudge.

The mouth was seen as a key part of the body for such a transformation.

"It was viewed as the main portal for the soul to leave the body upon death. Sometimes, the soul could come back to the body and re-animate it or else an evil spirit could enter the body through the mouth and bring it back to life," Read said.

Sep 15, 2011

An extraordinary collection of ancient feather fragments preserved in amber has opened a window into a lost world, one that now appears populated by dinosaurs covered in plumage as rich and varied as that of modern birds.

The feathers date to the end of the Cretaceous, about 85 to 70 million years ago. At that time, the forerunners of birds were well on their way to taking wing; dinosaurs like Epidexipteryx and Limosaurus, discovered in China in the last decade and dating to some 160 million years ago, possess relatively bird-like bone structures and hints of what might have been feathers.

Those hints have been interpreted -- and given life in eye-popping artist renditions -- as feathers, an interpretation that was plausible but still inconclusive.

But the latest fossils, found in Alberta and described Sept. 16 in Science, leave little doubt. The age of dinosaurs was a feathery one.

Remnants of a 20-foot extinct relative of crocodiles have been discovered in the same Colombian coal mine where Titanoboa, the world's largest snake, was found.

The findings, outlined in the journal Paleontology, suggest that members of these two predatory species might have fought to the death 60 million years ago. Titanoboa measured an incredible 42 feet long. ("Sue," the famous Tyrannosaurus rex specimen housed at the Field Museum, was about that long too.)

It sounds like the huge croc-like animal had an advantage over the snake, though. Its jaws alone were incredibly formidable.

"The younger individuals were definitely not safe from Titanoboa, but the biggest of these species would have been a bit much for the 42-foot snake to handle," lead author Alex Hastings, a graduate student at the Florida Museum of Natural History and UF's department of geological sciences, was quoted as saying in a press release.

There's little doubt that Acherontisuchus guajiraensis and Titanoboa competed for food. The former evolved to hunt and eat fish, which the snake also consumed. The genus, Acherontisuchus, is named for the river Acheron from Greek mythology, “the river of woe,” since the animal lived in a wide river that emptied into the Caribbean. Its snout was long, narrow and full of pointed teeth, perfect for grabbing lungfish and relatives of bonefish that inhabited the water.

The new species is a dyrosaurid, believed to mostly have been ocean-dwelling, coastal reptiles. The new adult specimens challenge previous theories the animals only would have entered freshwater environments as babies before returning to sea.

If you could stand on the surface of Kepler-16b, you'd have two shadows. At sunset, you would see an orange star about the size of the sun and next to it a much fainter red star. As the stars slipped toward the horizon, they would change places in the sky, like partners in a square dance.

You would not need to be Luke Skywalker visiting his home planet of Tatooine in the movie "Star Wars" to watch the twin sunset. The only science fiction in this story is how to make the 200 light-year journey to Kepler-16, a binary star system jointly sharing the Saturn-sized planet, Kepler-16b.

The finding, reported by scientists on NASA's Kepler planet-hunting space telescope team, adds a new page into Mother Nature's recipe book for extrasolar planets.

"It's the first one that circles two stars, so it's a fundamentally different kind of planet," lead researcher Laurance Doyle, with the SETI Institute in Mountain View, Calif., told Discovery News.

From a distance about as far as Venus orbits the sun, Kepler-16b circles both its parent stars in 221 days. The stars, which on average have about 21 million miles between them, fly around each other about every 41 days.

The whole system is perfectly aligned to Kepler's viewing spot, with the bodies crossing paths so that tiny amounts of their radiating starlight regularly, repeatedly and predictably vanish and reappear as the stars and the planet fly past one another.

The telescope points at a fixed position in space, looking for changes in light streaming from about 155,000 target stars in the constellations Cygnus and Lyra.

Because the Kepler-16 system is so perfectly aligned, scientists believe the planet formed alongside its parent stars from a common disk of gas and dust. The plane in which the two stars orbit is aligned within one-third of a degree of the orbit of the planet.

"Kepler himself would have been dizzy with excitement," he added, referring to the telescope's namesake, Johannes Kepler, the 16th century scientist who deduced the laws of planetary motion.

Both the Kepler-16 stars are smaller than the sun, so their planet lives largely outside the so-called habitable zone where liquid water could exist on its surface. Water is believed to be an essential ingredient for life as we know it.

The planet is estimated to experience temperatures that plummet from -100 to -150 degrees Fahrenheit (-70 to -100 degrees Celsius).

Timing also played a role in the discovery, notes Doyle. Computer models show that in early 2018, the planetary transits across the larger star will disappear from Kepler' view until around 2042. The passages across the smaller star's face, already slipping from view, will vanish in May 2014, and won't be back for 35 years.

Diamonds are a symbol of deep love. How deep? From the bottom of the ocean to the center of the Earth.

Rare “superdeep” diamonds may be formed as far down as 435 miles (700 kilometers) beneath the surface in the Earth's lower mantle.

But a recent discovery shows they didn't start out there. Some Brazilian superdeep diamonds may have begun as undersea lava flows. That means Earth's carbon cycle is involved in the process of recyling the diamonds and reaches far deeper than anyone previously knew, said researchers from the University of Bristol and the Carnegie Institution in the journal Science.

"This study shows the extent of Earth's carbon cycle on the scale of the entire planet, connecting the chemical and biological processes that occur on the surface and in the oceans to the far depths of Earth's interior," said Nick Wigginton, associate editor at Science in a news release.

The diamonds, from a mine near Junia, Brazil, showed the chemical fingerprint of basalt rock that forms on the ocean's floor from lava eruptions.

Jules Verne might say the rocks formed 20,000 leagues under the sea then journeyed to the center of the Earth.

Plate tectonics, movements of the Earth's crust caused by magma flowing underneath in the mantle, propelled the basalt downward into the lower mantle.

The basalt was then compressed into diamonds and returned to near the Earth's surface by magma plumes. The plumes hardened into diamond rich kimberlite deposits. The long-distance diamonds were then recovered by miners and studied by scientists.

"We looked at the variations in the isotopes of the carbon atoms in the diamonds,” said study co-author Steven Shirey of the Carnegie Institution in a press release.

“Carbon originating in a rock called basalt, which forms from lava at the surface, is often different from that which originates in the mantle, in containing relatively less carbon-13. These super-deep diamonds contained much less carbon-13, which is most consistent with an origin in the organic component found in altered oceanic crust," said Shirey.

The carbon signature told scientists the diamonds were made from surface lava flows, but now they had to prove they were formed deep beneath the surface. Most diamonds form at depth of less that 120 miles (200 km). Some form at deeper depths from surface rock, but until now, no lower mantle superdeep diamonds had been shown to form from surface rock.

To figure out just how deep the diamonds formed the researchers looked at inclusions, or tiny mineral deposits in the diamonds. They found inclusions with the chemical composition expected from melted and crystallized basalt. Basalt only forms those types of inclusions when it is produced under the extreme heat and pressure of the earth's lower mantle.

"I find it astonishing that we can use the tiniest of mineral grains to show some of the motions of the Earth's mantle at the largest scales," said Shirey.

Sep 14, 2011

Harboring a mistakenly inflated belief that we can easily meet challenges or win conflicts is actually good for us, a new study suggests. Researchers have shown for the first time that overconfidence actually beats accurate assessments in a wide variety of situations, be it sport, business or even war.

However, this bold approach also risks wreaking ever-greater havoc. The authors cite the 2008 financial crash and the 2003 Iraq war as just two examples of when extreme overconfidence backfired.

A team from the University of Edinburgh and the University of California, San Diego used a mathematical model to simulate the effects of overconfidence over generations. It pitted overconfident, accurate, and under-confident strategies against each other.

A paper published in Nature September 14 shows that overconfidence frequently brings rewards, as long as spoils of conflict are sufficiently large compared with the costs of competing for them. In contrast, people with unbiased, accurate perceptions usually fare worse.

The implications are that, over a long period of time the evolutionary principal of natural selection is likely to have favored a bias towards overconfidence. Therefore people with the mentality of someone like boxer Mohammad Ali would have left more descendents than those with the mindset of film maker Woody Allen.

The evolutionary model also showed that overconfidence becomes greatest in the face of high levels of uncertainty and risk. When we face unfamiliar enemies or new technologies, overconfidence becomes an even better strategy.

Long a symbol of the unattainable, blue roses will be for sale this fall in the United States and Canada.

Named “Applause,” the rose is genetically modified to synthesize delphinidin, a pigment found in most blue flowers. The rose was first released in in Tokyo in 2009, after 20 years of research by Suntory, a Japanese company that also distills whisky, and its Australian subsidiary, Florigene (now Suntory Flowers). Today Suntory announced the rose will be for sale at select florists in North America, beginning early November. While the flower might appear more silver-purple than sky-blue, Applause is the nearest to a true blue rose yet.

Arguably the world’s best loved flowers, humans have cultivated roses for more than 5,000 years. Roses can signify love, beauty, politics and war.

Blue roses have a mythic quality because they, until recently, were impossible to grow. Roses appear naturally in many shades of red, pink, yellow and white, but lack the natural ability to produce blue pigments. For centuries, blue roses have conjured unrequited love or the quest for the impossible.

Like a milk mustache that just won't go away, a shared genetic signature marks many Europeans and Indians as descendants from a common milk-drinking ancestor within the last 7,500 years.

The majority of Europeans and Indians who can drink milk share the mutation known as -13910T. Scientists already knew that the mutation was what allowed most European adults to drink milk.

“To our surprise we found that the -13910T mutation was also common in India – especially in those populations with a tradition of milk drinking,” said Toomas Kivisild of Cambridge University, senior author of the study, in a press release.

“Not only that, but by looking at nearby genetic regions we could show that the Indian -13910T has the same origin as that found in Europeans; that it could lead back to the same few people who may have migrated between Europe and India,” said Kivisild.

All human babies can drink milk because they produce an enzyme called lactase, which breaks down milk sugar or lactose. But only about a third of the world's adults can drink milk without suffering abdominal pain, bloating, nausea, diarrhea, and other symptoms of lactose intolerance.

The genetic mutation that allows adults to drink milk, called lactase persistence, seems to have evolved separately in Europe, Africa, and the Middle East. But until now, the source of lactase persistence in India, the world's largest drinker and producer of milk, was a mystery.

“India was an unknown quantity. But since lactase persistence had evolved independently in the Middle East and Africa, and because cattle had been domesticated independently in India around seven or eight thousand years ago, we were expecting to see uniquely Indian genetic causes,” said lead author, Cambridge’s Irene Gallego Romero.

As the advertisement says, milk does a body good. So good that the genetic mutation allowing milk drinking seemingly gave a survival advantage to lactose tolerant adults. The gene then spread through populations even if a large scale migration of milk drinkers didn't accompany the introduction of cattle.

“Genetic data doesn’t support some sort of large migration of people from Europe to India in the last 10,000 years. What’s more likely is that just a few migrants carried this mutation to India, and then it spread quickly,” said co-author Mark Thomas of University College London.

Sep 13, 2011

Exactly one year after the Tribute in Light at ground zero drew thousands of migrating birds into its beams, the night of September 11 passed without avian incident.

New York City Audubon volunteers who monitored the lights all night reported a peak of about 100 birds around 2 a.m., and about 700 altogether. It was a far cry from last year, when an estimated 10,000 birds were caught over the course of the night, circling in confusion until the lights were temporarily shuttered five separate times.

That night was almost perfectly designed to lure birds traveling down the Atlantic Flyway, one of North America’s four major conduits for birds migrating to South and Central America. Several nights of storms kept birds grounded in the wetlands north of New York City; on the night of Sept. 11, a favorable tailwind released them, but dense cloudcover hid the stars birds use to navigate and calibrate inborn geomagnetic compasses. The Tribute in Light’s bank of 88 7,000-watt xenon searchlights dominated the sky.

“Attraction to light is deep in the ancestral instinct, especially in a situation where there’s cloud cover,” said ornithologist Andrew Farnsworth of Cornell University. “A bright light trumps all.” In the birds came.

Though not in direct physical danger from the lights, a night spent circling can be tiring. In previous years, before the New York Audubon Society started monitoring the lights, reports of Manhattanites waking to find exhausted migrants resting on their balconies were not uncommon.

On this Sept. 11, very different conditions prevailed, said Farnsworth. The weather over several previous nights was favorable for flight, so there was no buildup. On the night of 9/11, light winds from the south, blowing against the birds, discouraged flight. “It’s early in the season,” Farnsworth said. “They’re in no tremendous rush.”

The night was partially cloudy, but not so cloudy as to confuse birds, which last year included various species of tanagers, warblers, thrushes and orioles. The 2 a.m. buildup occurred during a moment of cloudiness, but “the moon popped out for a second, and away they went,” said New York City Audubon volunteer Adriana Palmer.

Modern humans may have some traces of genes from Neanderthals, but a new study suggests any breeding between the two was most likely a rare event.

The new computational model, based on DNA samples from modern humans in France and China, shows successful coupling happened at a rate of less than 2 percent.

The research suggests that either inter-species sex was taboo, or that the hybrid offspring had trouble surviving, according to the findings in the Proceedings of the National Academy of Sciences.

There may have been "extremely strong barriers to gene flow between the two species because of a very low fitness of human-Neanderthal hybrids, a very strong avoidance of interspecific mating, or a combination," say study researchers at the University of Geneva and the University of Berne in Switzerland.

Between two and four per cent of the human genome can be linked to the long-extinct Neanderthals and their cavemen relatives.

The squat, low-browed Neanderthals lived in parts of Europe, Central Asia and the Middle East for up to 300,000 years. But all evidence of them disappears some 40,000 years ago, their last known refuge being Gibraltar.

Why they died out is a matter of some debate, because they co-existed alongside modern humans.

A study by French researchers published in the journal Science last month suggested that modern humans gleaned a competitive immune advantage from their liaisons with cavemen.

The dusky grouper, one of the major predators in the Mediterranean sea, used to be so large in antiquity that it was portrayed as a "sea monster," a new study into ancient depictions of the endangered fish has revealed.

"Amazingly, ancient mosaic art has provided important information to reconstruct this fish's historical baseline," Paolo Guidetti of the University of Salento in Italy, told Discovery News.

Considered one of the most flavorful species among the Mediterranean fish, the dusky grouper (Epinephelus marginatus) is a large, long-lived, slow-growing, protogynous hermaphrodite fish (with sex reversal from female to male). It can be found mainly in the Mediterranean, the African west coast and the coast of Brazil.

Having faced harvesting for millennia -- grouper bones have been found in human settlements dating back more than 100,000 years -- this species has been decimated in recent decades by commercial and recreational fishing. It is now categorized as endangered on the International Union for Conservation of Nature (IUCN) Red List.

The recovery of endangered fish species requires a careful evaluation of some key elements, such as abundance, size structure, and spatial distribution. Such evaluation usually involves comparing unfished areas with unprotected sites.

"But most such marine protected areas are too small and 'young' (established a few decades ago, at most) to provide information on 'pristine' conditions," Guidetti and colleague Fiorenza Micheli, a professor of marine ecology at Stanford's Hopkins Marine Station, wrote in the current issue of Frontiers in Ecology and the Environment.

To look farther back into the grouper's history, the researchers examined hundreds of Etruscan, Greek, and Roman paintings and mosaics depicting fishing scenes and fish.

At the end, they focused on 23 mosaics which represented groupers. In 10 of the 23 mosaics, dating from the 1st to 5th centuries, groupers were portrayed as being very large.

Indeed, the ancient Romans might have considered groupers some sort of "sea monsters" able to eat a fisherman whole, as shown in a 2nd century mosaic from the Bardo National Museum in Tunis.

The mosaics also indicated that groupers lived in shallow waters much closer to shore, and were caught by fishermen using poles or harpoons from boats at the water's surface.

"It's a technique that would surely yield no grouper catch today," said the researchers.

Although there are no known instances of dusky groupers attacking human swimmers, the art depictions are very "informative," said the researchers.

"These representations suggest that groupers were, in ancient times, so large as to be portrayed as sea monsters and that their habitat use and depth distribution have shifted in historical times," Guidetti and Micheli wrote.

Long before dinosaurs, something was digging intricate homes and roads underground.

While life on Earth 240 million years ago flourished in the seas and on land, the underground worlds discovered in Morocco are the oldest examples of such communal subterranean structures from a low-latitude area.

The burrows, described in the latest issue of the journal Palaios, are the world’s second-oldest known communal burrows. The oldest, from South Africa, predate these by only 5 million years.

It's possible that a similar animal created both structures.

"You should imagine the tracemaker as a stout, short-bodied, four-legged animal with a short tail and short neck," lead author Sebastian Voigt told Discovery News. "The trunk was about 20-25 centimeters (8-10 inches) in length. We have to assume that it had five sturdy digits with claws suitable for digging into moderately soft sediment."

Funded by the German Research Foundation, ichnologist Voigt from the Institute of Geology at TU Bergakademie Freiberg and his colleagues studied the burrows, located in red beds of the Argana Basin in central Morocco. The architecture consists of numerous openings, exists, tunnels and chambers.

"The Argana burrows do not have any equivalent in the fossil record or among extant burrowing vertebrates," Voigt said. "Their chambers are exceptionally complex structures and two-fold winded tunnels have never been observed anywhere else."

Based on this arrangement and what can be inferred about the burrow makers, the scientists think the underground world served as a retreat, permitting escape from predators. Although dinosaurs were not yet around, huge, fast-running crocodiles with long legs were in the area, as evidenced by fossil finds. Close relatives of today's lizards, snakes and tuataras were also around, along with relatives of birds and dinosaurs.

The site's geology, as well as the burrow's design, also suggests the animals headed underground to tolerate weather extremes.

"During the Triassic, the region probably was a semi-arid large inland basin," Voigt explained. "Rivers were slowly flowing after episodic rain fall. Streambeds were flat and completely dry for lengthy periods. Loose vegetation covered the banks of the streams. It was hot during the day and cold in the night."

The smooth floor of the tunnels reveals they were well used, with the animals probably gathering food, such as plants, roots and insects, at the surface during nighttime.

Burrows made by individual animals, such as fish, date to early Paleozoic periods, indicating this behavior was very important since practically the beginning of complex animal life on the planet. Voigt suspects it first evolved to permit escape from environmental extremes, particularly drought.

It seems that whenever animals could dig to escape, they did. Some dinosaurs dug burrows. One of the limitations is having the right substrate. In the case of the Moroccan animals, the conditions were perfect for digging. The burrows there were constructed in riverbank sandy substrates intermixed with moist overbank mud.

Sep 12, 2011

On Sunday, with the opening of the memorial at Ground Zero, there was finally a place to go, to a name carved in bronze, one among almost 3,000.

They could not keep their hands from them, tracing the letters with their fingers, lingering over the one remaining physical token of the loved ones they lost forever in the explosive force of the 9/11 attacks.

Given access to the memorial for the first time on Sunday, some of the families stroked the engravings, as if administering comfort.

Robert Peraza lost his son Robert on September 11 2001. He was a trader with Cantor Fitzgerald in the North Tower of the World Trade Centre, just 30 years old. He and 657 other employees of the investment bank died in the holocaust.

Mr Peraza had watched the collapse of the towers on television. Robert was in the prime of life, a rugby player and marathon runner. Only a month before his death he had sent his parents a four-page letter explaining how happy he was. On Sunday, Mr Peraza knelt at his son's name, his head bowed in quiet remembrance, his eyes closed tightly and his left palm placed over the words "Robert David Peraza".

The North Tower is now the North Pool, the square pit that held its foundations here a four-sided fountain feeding a reflecting pool that sits within the tower's footprint. The names line the sides, overlooking the water.

The gaps in the bronze met the modest title and theme of the memorial: "Reflecting Absence".

While many were simply happy to take solace in the act of touching their loved ones' names, some relations placed the Stars and Stripes in the grooves of the letters, others flowers. Many made rubbings to take home, to frame perhaps, or put away for some moment of solitary reflection.

A woman kissed the name of Steven John Mercado, only 38 years old and one of 343 members of the Fire Department of New York who perished on that Tuesday morning. Photographs, letters and firemen's helmets were placed next to other names.

Of the 2,753 people consumed in the collapse of the Twin Towers 1,124 have no resting place, pulverised into extinction or consumed by a jet fuel fire that softened steel.

August Larsen, just nine years old, was one of those making a crayon rubbing, in his case of the name of his father, Scott Larsen, a firemen who died when the South Tower collapsed. August was born only a few days after his father’s death.

As he attempted to connect with the father he never knew yesterday, the names of the victims were being read out by relations. From Gordon Aamoth to Igor Zukelman, no one was forgotten.

For more than three hours it continued to the accompaniment of classical music. Some of those doing the reading had been too young to know the mothers or fathers they lost that day.

Peter Negron returned to Ground Zero eight years after he had stood there as a nervous 13-year-old boy, reading a poem about the stars that comforted him in the nights after his father was stolen.

“Shining through the dark, they calmly stayed and gently held me in their quiet way,” he had said then. “I felt them watching over me, each one. It let me cry and cry until I was done.”

Mr Negron surveyed Ground Zero on Sunday as a man of 21, speaking of his regret for the rites of passage he should have shared with Pete Negron, a 34-year-old environmental worker from New Jersey, whose desk was on the 88th floor of the World Trade Center.

“I’ve stopped crying but I haven’t stopped missing my dad,” he said. “I wish my dad had been there to teach me how to drive, ask a girl out on a date, see me graduate from high school,” he said, before telling how he had become a father figure to his brother Austin, who was two at the time of the attacks.

“I try to teach him all the things my father taught me: how to catch a baseball, how to ride a bike, and to work hard in school.”

Even in disaster some good comes, friendships forged between those thrown together by grief, for example. The names of Christopher Epps and Wayne Russo sit side by side on the memorial. Christopher, 29, an employee of Marsh and McLennan, and Wayne, 37, another employee of the firm, did not know each other.

Their families met after their deaths, and so close did their bond become that they chose to place their names together.

“It’s the closest I’ll ever get to her again,” said Mary Dwyer of her sister, Lucy Fishman. Lucy was 36 when she died in the South Tower.

“It’s peaceful,” said Trisha Scudder, of Pennsylvania, as she studied the name of her brother, Christopher Clarke, a bond salesman. “I wish I wasn’t seeing his name, though.”

The panels carrying the names are backlit so they can be read at night, and their temperature is controlled so that they are comfortable to the touch.

“I feel so happy this has been put together,” said Peter Rauss, a 19-year-old medical student from New York, as he stood by the name of his uncle, Philip Ognibene, a stockbroker.

The day itself on Sunday had begun, like that fateful day a decade earlier, with blue sky. Silence fell across Manhattan at 8.46am, 10 years exactly from the moment when American Airlines Flight 11, a Boeing 767, struck the North Tower. For 17 minutes it was a terrible, inexplicable accident – until United 175, another fuel-laden 767 flew into the South Tower.

There were four silences marking the impacts of the airliners that day, the third, American 77 at the Pentagon and the fourth, United 93, at Shanksville, Pennsylvania. Two more followed marking the collapse of the towers.

Each silence was broken by the reading of more names, a steady drumbeat of sorrow until all 2,982 who died on September 11 and in the 1993 World Trade Centre bombing had been remembered.

It took 10 minutes from Gordon Aamoth Jr, a 32-year-old investment banker, to the end of the As. Finally, more than three hours later, came Igor Zukelman, a 29-year-old Ukrainian wealth manager.

Readings were given by the statesmen who guided New York and the US through their darkest hours, and those attempting to steer America through the doldrums it has never really escaped.

“We will not fear, even though the Earth be removed, though the mountains be carried in the midst of the sea,” said President Barack Obama, reading from the 46th Psalm.

George W Bush read from a letter sent in November 1864 by Abraham Lincoln to Lydia Bixby, a widow from Boston who had lost five sons in the Civil War.

“How weak and fruitless must be any words of mine which should attempt to beguile you from the grief of a loss so overwhelming,” Lincoln wrote. “But I cannot refrain from tendering to you the consolation that may be found in the thanks of the Republic they died to save.” Christine Box, whose brother Gary was a fireman, clutched a photograph of him running to the scene. “He answered his last call,” it said.

“I have to be here,” said Daniela Notaro, who lost her sister Rosaria Reneo. “It’s where she never came home from”.

“It will never feel like 10 years,” said Mary Beth Dougherty, mourning her brother Kevin Murphy. “It’s just that the children have gotten older”.

For some, the horror of that day has dimmed not at all. The memorial may bring closure of sorts.

“There has been no escape,” said Victor Colaio, who lost his sons Stephen and Mark, both brokers with Cantor Fitzgerald.

“There’s just nowhere to go. If you sit down to eat, it’s purely to sustain yourself. The taste is not the same.